Malignant tumors are often treated by surgical resection of the tumor to remove as much of the tumor as possible. Infiltration of the tumor cells into normal tissue surrounding the tumor, however, can limit the therapeutic value of surgical resection because the infiltration can be difficult or impossible to treat surgically. Direct chemo-drug (anticancer drug) delivery therapy and radiation therapy are the two common post-resection treatment methods used to supplement surgical resection by targeting the residual malignant cells after resection, with the goal of sterilizing them, reducing the rate of recurrence, and/or delaying the time to recurrence. Radiation therapy can be administered through one of several methods, or a combination of methods, including permanent or temporary brachytherapy implants, and external-beam radiation. Direct chemo-drug delivery therapy is typically administered by inserting a catheter device into the resected cavity and infusing chemo-drugs through a lumen in the catheter and into the resected cavity where the drugs diffuse into the surrounding tissue. In some cases, direct chemo-drug therapy is applied to a tumor without resection in order to shrink the tumor prior to resection, or in the case of where surgery is contraindicated (e.g. inoperable tumors).
However, in certain treatment areas of the body, it is very difficult for the drugs to penetrate the target tissue (either a tumor itself, or the tissue surrounding the area of a resected tumor). For example, it is difficult for large molecule drugs to penetrate the brain parenchyma when treating brain tissue. Thus, in these situations, the chemo-therapy does not treat a sufficient thickness of tissue (typically 1-2 cm) to target the residual malignant cells. In order to improve drug penetration in these types of situations, a method of directly delivering the drugs to the target tissue under positive pressure has been developed. This method is commonly referred to as convection-enhanced delivery (CED). CED uses continuous positive pressure drug infusion to generate a pressure gradient to cause the drug to diffuse into the desired thickness of target tissue.
However, current methods and devices have several drawbacks. For one, at some point during infusion, the drugs tend to leak out of the target volume (the volume of target tissue) through the space in the tissue created by the catheter. The drugs can then follow the catheter pathway through the tissue and out of the patient's body. Moreover, once this occurs, it is difficult to maintain the pressure gradient within the target volume resulting in ineffective drug penetration into the target tissue.
Accordingly, there remains a need for methods and devices which can provide for effective direct delivery of drugs under continuous positive pressure drug infusion.